2008 年 46 巻 6 号 p. 647-654
Transcatheter arterial embolization (TAE) is a way of occluding blood vessels such as arteriovenous fistula that are physiologically unnecessary. Although this technique becomes more popular in clinical practice for its minimal invasiveness, it is sometimes fraught with difficulties especially when a catheter cannot be placed directly in a target vessel. The risks associated with TAE may be reduced by better understanding of flowing behaviors of embolic agents in blood vessels. In the present study, we established a numerical model to simulate TAE and investigated influences of injection positions and intervals of spherical embolic agents (SEAs) on their flowing behaviors. Flows of blood and SEAs were modeled by the equation of continuity along with the Navier-Stokes equation, re-formulated based on the moving-particle semi-implicit method where continuum is represented by collective behaviors of particles. An SEA was modeled as an aggregate of particles. Particles consisting of the membrane of SEA were linked by springs which resist to stretching and bending. Based on the virtual work principle, a force acting on the SEA membrane was calculated. Using this numerical model we simulated injection of SEAs into a T-junction blood vessel where a target vessel to be occluded with SEAs is connected perpendicularly to a main vessel. The simulation showed that a distribution ratio of SEAs between the main and target vessels did not always coincide with a distribution ratio of blood flow evaluated in the absence of SEAs. Although the proximal variations of the injection positions were less influential, the radial position of injection significantly affected the flowing behavior of SEAs. Frequent injection of SEAs induced jam of SEAs in the target vessel, causing undesired flowing of SEAs into the main vessel. These results indicated the significant influence of injection position and interval on flowing behavior of SEAs.